Hitherto unnoticed biogenic volatile iodated hydrocarbons have been determined in open ocean and coastal surface waters. The results indicate that iodated substances are produced by planktonic organisms rather than by macroalgae. It is shown that the diversity of iodated organic compounds released in the seawater is larger than was previously suggested. In the global cycling of iodine it is neceassary to consider organic compounds other than methyl iodide.